Sprout control of harvested tubers, in particular of potatoes, is an important part of potato storage which allows for subsequent distribution to potato processors for French fry production, and to grocery stores and restaurants of a satisfactory food product months beyond harvesting, skin formation and dormancy. Potato sprout control is particularly important to maintain the desired texture and sugar content of the harvested potatoes.
In potatoes, cell division and cell elongation of the tuber buds results in formation and emanation of sprouts from the tuber buds after the potato has entered a quiescent phase of dormancy that typically follows storage at or slightly above 45.degree. F. Although tuber sprout formation can be suppressed by storage of the tubers at lower temperatures of from 38.degree. to 39.degree. F., the lower storage temperatures cause increased reducing sugar levels in the stored potatoes. Potatoes with increased levels of reducing sugars may turn brown when french fried, thereby producing an unacceptable food product.
To inhibit sprout formation in potatoes, synthetically derived sprout inhibitors, for example, tetrachloronitrobenzene, maleic hydrazide, and isopropyl-3-chlorophenylcarbamate (CIPC) also commonly referred to as chlorpropham, have been applied. CIPC is typically applied in one or two applications to the tubers to be stored using thermal fogging techniques. Conventional thermal fogging involving the application of CIPC into a stream of hot air or onto a hot surface of up to 1000.degree. F., to produce a CIPC aerosol. The CIPC aerosol is circulated through potatoes piled in a potato storage building with the use of fans. Preferably the potatoes are firm rather than soft when treated with the CIPC aerosol, since a pile of softened potatoes may be substantially compressed, thereby impeding distribution of the aerosol. CIPC residue levels, will, however, typically decrease over time due to biodegration, venting and atmospheric loss. To extend the effective sprout inhibiting capability of CIPC, further applications may be needed.
However, it is becoming increasingly desirable worldwide to decrease the application of synthetically derived substances to fruits and vegetables during growth, storage and shipping. In particular, residue levels of CIPC are subject to regulation. So, while CIPC has been utilized to inhibit sprout formation in tubers for decades, its toxicology has been questioned and it is one of a number of synthetically derived substances whose residue levels are of concern to the U.S. Environmental Protection Agency.
In order to decrease use of synthetically derived substances such as CIPC, naturally occurring biological control mechanisms and substances are actively sought. Naturally occurring sprout inhibitors are known. For example, U.S. Pat. No. 5,436,226 for NATURAL SUPPRESSION OF SPROUTING IN STORED POTATOES USING JASMONATES claims a method of inhibiting sprouting of tubers by exposure to various forms of jasmonic acid, at some of which are naturally occurring compounds.
Also by way of example, Canadian Patent No. 1,203,394 teaches the use of dimethylnaphthalene (DMN) and diisopropylnaphthalene (DIPN) as potato sprout inhibitors. However, this patent teaches the need for application of DMN and DIPN with an inert carrier which implies the utility of DMN and DIPN alone as the active ingredient. However, long term effectivity of DMN and DIPN as tuber sprout inhibitors at lower residue levels under less than ideal circumstances has not been fully established.
It is against this background that the significant improvements and advancements of the present invention have taken place.